flexray – a communications network for automotive control

Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2005.

TM

FlexRay – A Communications Network for Automotive Control SystemsWFCS 2006

Rainer MakowitzAutomotive Systems Engineering, EMEA

TM Freescale Semiconductor Confidential and Proprietary Information. Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2005.

Slide 1

FlexRay is the next generation automotive bus to provideHigh-speed communicationDeterministic communicationFault-tolerant communication

FlexRay System Components released by the FlexRay Consortium in 2005:

• FlexRay Communications System Protocol Specification Version 2.1, May 2005

• FlexRay Communications System Electrical Physical Layer Specification 2.1, May 2005

• FlexRay Bus Guardian Specification Version 2.1, December 2005

The FlexRay Standard


Slide 2

In addition:• FlexRay Executable (Reference) Model, Version 2.1.0.2

available today from FSLcertified by TUEV SystemC basedUnambiguous reference for FlexRay IP providers and tool makers

FlexRay Consortium Web site: http://www.flexray.com/Freescale Web site: http://www.freescale.com/flexray

The FlexRay Standard


TM

Evolution of Vehicle Networks


Slide 4

Evolution of Vehicle Networks (1)

• CAN 1st car use 2002; widely adopted in automotive productsCAN-B (ISO 11898-3): 125kbps, VUL=1.5V, VUH=3.5VCAN-B (SAE J2411): 33kbps, VUL=0V, VUH=4.1V CAN-C (SAE J2284): 500kbps, designed limit of 1 Mbps rarely implemented today

• Byteflight1st car use for airbag in 200410MbpsTime-triggered + Flexibility

• FlexRay1st car use for Chassis application in 200610MbpsTime-triggered + Flexibility + safety concept


Slide 5

Byteflight Data Transfer Overview

• Master clock• Cycle starts w/ Sync symbol• Fixed time slots for high priority communication• Rest of bandwidth is allocated to low priority communication

SyncSymbol

SyncSymbol

• Frame format: 6bit Sync, ID Byte, 12 message Bytes, 2 CRC Bytes


Slide 6

FlexRay Data Transfer Overview

• 254 bytes, 8 Bytes overhead (5 header incl. header CRC, 3 frame CRC) plus start/stop bits

CRC CRC

24 bits

Data nFrame ID

7 bits 0 ... 254 Bytes

Cyclecount CRC

FlexRay Frame 5 + (0 ... 254) + 3 Bytes

Payloadlength

11 bits 6 bits

Sync

fram

e in

dica

tor

11 bits

HeaderCRC

Nul

l fra

me

indi

cato

r

Header Segment Payload Segment Trailer Segment

Data 0 Data 1

Header CRCCovered Area

Payl

oad

prea

mbl

e in

dica

tor

Res

erve

d bi

t

11111

Data 2

Star

tup

fram

e in

dica

tor


Slide 7

FlexRay Data Transfer Overview

2

2

3

3

4

4

5

5

6

6

7

8

8

9

1

1

9

13

Static segment –TDMA based MAC

(bounded latency and small latency jitter communication,deterministic communication

static bandwidth requirements)

1d

3d

3e

4b1c

1c

3c

3c2a

1a

1b

Cha

nnel

AC

hann

el B

4a

Communication cycle

(driven by synchronized time base)

t

t

7

3a

NIT

3b 2b

Dynamic segment –flexible TDMA based MAC

(ad-hoc communication,varying bandwidth

requirements,)

Example of a FlexRay communication cycle showing the static and the dynamic segment.


Slide 8

Evolution of Vehicle Networks: Issues Resolved

CAN byteflight FlexRay

Unpredictable latency

TDMA + Bandwidth Allocation Flexibility

TDMA + Bandwidth Allocation Flexibility +

Fault tolerance concept


Slide 9

Evolution of Vehicle Networks (Overview)

Feature CAN TTP byteflight FlexRay

Message transmission asynchronous synchronous synchronous and asynchronous

synchronous and asynchronous

Message identification message identifier time slot message identifier time slot Data rate 1 Mbps gross 2 Mbps gross 10 Mbps gross 10 Mbps gross

Bit encoding NRZ with bit stuffing modified frequency modulation (MFM)

NRZ with start/stop bits

NRZ with start/stop bits

Physical Layer transceiver up to 1 Mbps not defined optical transceiver up

to 10 Mbps 10Mbps with differential signalling

Clock synchronization not provided distributed, in µs range

by master, in 100 ns range

distributed, in µs range

Temporal composability

not supported supported supported for high priority messages supported

Latency Jitter bus load dependent constant for all messages

constant for high priority messages according t_cyc

constant for all messages

Error containment not providedprovided with special physical layer

provided by optical fiber and transceiver

provided with special physical layer

Babbling idiot avoidance

not provided only by independent bus guardian

provided via star coupler

provided via star coupler or bus

Extensibility excellent in non-time critical applications

only if extension planned in original design

extension possible for high priority messages with effect on bandwidth

separation of functional and structural domain

Flexibility flexible bandwidth for each node

only one message per node and TDMA cycle

flexible bandwidth for each node

multiple slots per node, dynamic


TM

Fault Tolerance


Slide 11

FlexRay and Functional Safety

• Safety requirementsDepend on application area (brake, steering, driver assist)Lead to redundancy of system componentsDegree of redundancy must be calibrated by field data on failureprobability

• FlexRay provides the infrastructured to design reliable (safety-critical) communications systems

Deterministic System DesignStatic Segments Dual channel - scalable system fault-tolerance Bus GuardianInterconnect topologies: centralized or bus


Slide 12

Fault-Tolerance Overview

Scalablefault-tolerance

to supportfault-tolerant and

non fault-tolerant systems

Scalablefault-tolerance

to supportfault-tolerant and

non fault-tolerant systems

Fault-tolerant clock synchronization also usable in a non fault-tolerant way

Topological flexibility(single versus dual channel,mixed connectivity)

Conceptual separation of functional and structural domain


Slide 13

Topological Flexibility

passive medium,most experience,

cost efficient

passive medium,most experience,

cost efficient

allows forhigh data rates,increases error

containment

allows forhigh data rates,increases error

containment

reducedwire-harness,

experience, cost

reducedwire-harness,

experience, cost

tolerates one faulty channeltolerates one faulty channel

SinglechannelSinglechannel

DualchannelDualchannel

BusBus Multiple starMultiple star

electrical &opticalphysical layer

electrical &opticalphysical layer

mixed topologies

mixed topologies

@ 10MBit@ 10MBitOptional BGOptional BG


Slide 14

• Exchanging DeviationsImplicit exchange of clock deviations via exchange of (sync) frames

• Reference clock No single physical reference clock existsEach node calculates deviation in respect to a virtual referenceclockVirtual reference clock established using distributed fault-tolerant clock synchronization algorithm (fault-tolerant midpoint)Combined use of offset correction and rate correction

Clock Synchronization Principle

Send frame A Send frame C

1:00 2:00 3:00

Receive frame BNode x

2:00 (expected time of arrival)

Receive frame B(0:05) (measured deviation)

2:05 (actual time of arrival)


Slide 15

Separation of Functional & Structural Domain

2

2

3

3

4

4

5

5

6

6

7

8

8

9

1

1

9

13

Static segment –TDMA based MAC

(bounded latency and small latency jitter communication,deterministic communication

static bandwidth requirements)

1d

3d

3e

4b1c

1c

3c

3c2a

1a

1b

Cha

nnel

AC

hann

el B

4a

Communication cycle

(driven by synchronized time base)

t

t

7

3a

NIT

3b 2b

Dynamic segment –flexible TDMA based MAC

(ad-hoc communication,varying bandwidth

requirements,)

Example of a FlexRay communication cycle showing the static and the dynamic segment.


Slide 16

Functionality Beyond FlexRay

• Low Protocol Overhead Services to support application safety are left to the application software (eg. membership services)AutOsar must complement FlexRay link layer (in the controller)

FlexRay ECUFlexRay ECU

Communications protocolCommunications protocol

ApplicationApplication

Application related fault-tolerance (such as message agreement)

Application related error handing(such as system diagnosis)

-> Functional or structural view

Communication rel. fault-tolerance (such as clock-synchronization)

Communication rel. error handing(loss of synchronization)

Error signaling to application

-> Functional view


TM

Applications


Slide 18

Application Domain Examples

PowertrainPowertrain

2008

ChassisChassis2006

By-wire systemsBy-wire systems

2012

High-speed CANreplacement

High-speed CANreplacement

2008

BackboneBackbone

2008


Slide 19

Example: Chassis Applications

• Adaptive Suspension SystemDistribution of control algorithm between 4 wheel nodes and 1 control unitPassive star topology @ 10MbpsSingle channelFail silent strategy

WheelUnit

WheelUnit

WheelUnit

WheelUnit

Passive Star

ControlUnit

FlexRay

FlexRay

FlexRay ECU based on MPC563 and MFR4200.


Slide 20

Trends in Chassis Electronics

• Current state: Longitudinal dynamics only (ABS and Traction control)

• Future: Networking of Longitudinal & Lateral Dynamics & Driver Assistance

• Challenge: Flexible architecture w/ > ABS, DSC in basic configuration> Active Steering, electric brake management, ACC as options

FlexRay provides a feasible backbone w/ separation of structure and function> No change of ECU code at change of option package> All ECUs have FlexRay slots assigned according to platform plan


Slide 21

Example: X-by-Wire

• European funded project SPARC (Secure Propulsion Using Advanced Redundant Control)

Execution layer (steering system, braking system, power pack (engine & transmission), energy system) uses FlexRay as bus architecture Implementation of steer-by-wire system, brake-by-wire system, shift-by-wire system, engine-by-wire system, load separation module and energy managementThe platform is equipped with two independently working FlexRay Buses, each consisting of two channels. One is assigned to the communication between the HMI and the DCS, the other bus is used for communication between the PTC and the execution (mechatronic) layer, i.e. the lower part of the hourglass.

Command Layer

Execution Layer


Slide 22

SPARC Architecture

PowerModule A

Brake A1 Brake A2 Brake A3

PowerModule BJoystick B

Central ECUs StarJoystick A

Brake B1 Brake B2 Brake B3

Star

Camera, GPSRadar

PowerModule A

Brake A1 Brake A2

PowerModule BJoystick B

Central ECUs StarJoystick A

Brake B1 Brake B2

Star

Camera, GPSRadar

Truck

Car


TM

FlexRayProduct History


Slide 24

FlexRay Implementations Roadmap

Freescale SemiconductorCommunication ControllersFreescale SemiconductorCommunication Controllers

FlexRay ProtocolSpecificationsFlexRay ProtocolSpecifications

2000 2001 2002 2003 2004

PS V0.4.3

PS V0.6

PS V0.8

PS V1.0

PS V1.9

FPGAV4FPGA

V5FPGA

V9

MFR4100 MFR

4200

PS V2.0

FlexRayConsortium

founded

Philips SemiconductorsPhysical Layer Bus DriverPhilips SemiconductorsPhysical Layer Bus Driver

TJA1080

2005 2006

PS V2.1A

MFR4300

Integrated MCUsw/ FlexRayfrom many vendors

FlexRay IPModules


Slide 25

Summary

• FlexRay is the next generation communication backbone for automotive applications

Qualified Controller and Physical Network Interface products existAutomotive mass-production SOP 2006Reference Model to explore systems architecture

• Safety critical applications like by-wire systems will use mechanisms built into FlexRay to support fault tolerance

No technical limits for state-of-the-art systemsFull flexibility for emerging systems architectures for ‘affordable’safety in vehicles

• FlexRay market will develop in non-safety-critical application first

Freescale Semiconductor Confidential and Proprietary Information. Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2005.

Thank you

for your attention

www.freescale.com

flexray – a communications network for automotive control

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